1. Field of the Invention
The invention relates in general to an apparatus and a method for timing error detection decision lock, and more particularly to an apparatus and a method for the reliable timing error detection decision lock.
2. Description of the Related Art
FIG. 1 (Prior Art) is a block diagram showing a conventional apparatus 100 for timing error detection decision lock. Referring to FIG. 1, the conventional apparatus 100 includes a lock detector 110, a mean unit 120 and a decision unit 130. The lock detector 110 obtains multiple detected values from a transmission signal. The mean unit 120 receives the detected values, and averages every N detected values to obtain multiple means. For example, the mean unit 120 averages the detected values d1 to d4 to obtain a mean a1, and averages the detected values d5 to d8 to obtain a mean a2, and so on.
The decision unit 130 determines whether the means obtained by the mean unit 120 are greater than a detected threshold value or not. FIG. 2 (Prior Art) is a schematic illustration showing a conventional decision lock. In FIG. 2, when the means are greater than a detected threshold value LTH, the decision unit 130 determines the transmission signal as in a timing-lock status. However, the output of the mean unit 120 tends to be affected by the external factors, such as noises, frequency offsets or neighboring channels, so that the decision unit 130 has the incorrect determination. In addition, if the detected threshold value LTH is set to be too low, then the transmission signal, which has not yet entered the timing-lock status, may be incorrectly determined, by the decision unit 130, as in the timing-lock status. On the contrary, if the detected threshold value LTH is set to be too high, then the transmission signal, which has entered the timing-lock status, cannot be correctly determined as entering the timing-lock status. Thus, the decision unit 130 has to set different detected threshold values LTH corresponding to various conditions, and the constant detected threshold value LTH cannot be adopted to handle all the conditions.